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Cold-formed rack profiles are produced mainly for use in industrial storage systems. Their complex geometry and the presence of hole patterns along their length make the strength prevision of these structural elements difficult. This article evaluates the safety presented in the design of rack columns by adaptations of the Direct Strength Method (DSM), the original formulation of which does not address perforations. The safety parameters used here are the reliability indexes, calculated by the First Order Second Moment (FOSM) method, used in the calibration of the AISI S100 current standard, the First Order Reliability Method (FORM) and Monte Carlo Simulation. Only methodologies that applied the reduced thickness method in cross-section modelling produce results close to the target reliability indexes suggested for cold-formed columns. The target indexes are met for all load combinations when only distortional buckling failure is considered. However, the DSM adaptations are still imprecise when considering failure with local buckling. New professional factors were calibrated for these cases, as the design using the current $\phi =0.85$ ϕ = 0.85 does not meet the safety requirements. [ABSTRACT FROM AUTHOR]

[Display omitted] Cells respond to the stiffness of their surrounding environment, but quantifying the stiffness of a fibrous matrix at the scale of a cell is complicated, due to the effects of nonlinearity and complex force transmission pathways resulting from randomness in fiber density and connections. While it is known that forces produced by individual contractile cells can stiffen the matrix, it remains unclear how simultaneous contraction of multiple cells in a fibrous matrix alters the stiffness at the scale of a cell. Here, we used computational modeling and experiments to quantify the stiffness of a random fibrous matrix embedded with multiple contracting inclusions, which mimicked the contractile forces of a cell. The results showed that when the matrix was free to contract as a result of the forces produced by the inclusions, the matrix softened rather than stiffened, which was surprising given that the contracting inclusions applied tensile forces to the matrix. Using the computational model, we identified that the underlying cause of the softening was that the majority of the fibers were under a local state of axial compression, causing buckling. We verified that this buckling-induced matrix softening was sufficient for cells to sense and respond by altering their morphology and force generation. Our findings reveal that the localized forces induced by cells do not always stiffen the matrix; rather, softening can occur in instances wherein the matrix can contract in response to the cell-generated forces. This study opens up new possibilities to investigate whether cell-induced softening contributes to maintenance of homeostatic conditions or progression of disease. Mechanical interactions between cells and the surrounding matrix strongly influence cellular functions. Cell-induced forces can alter matrix properties, and much prior literature in this area focused on the influence of individual contracting cells. Cells in tissues are rarely solitary; rather, they are interspersed with neighboring cells throughout the matrix. As a result, the mechanics are complicated, leaving it unclear how the multiple contracting cells affect matrix stiffness. Here, we show that multiple contracting inclusions within a fibrous matrix can cause softening that in turn affects cell sensing and response. Our findings provide new directions to determine impacts of cell-induced softening on maintenance of tissue or progression of disease. [ABSTRACT FROM AUTHOR]

This paper describes an experimental investigation of a novel reinforced concrete buckling-restrained brace for precast concrete lateral load-resisting frame structures in seismic regions. The proposed brace uses ductile reinforcing bars with unbonded lengths across end gaps and bonded lengths at the middle region for lateral stiffness, strength, energy dissipation, and ductility. The experimental program included four isolated diagonal brace subassemblies subjected to reversed-cyclic pseudostatic lateral loading. Local buckling of the energy-dissipation bars across the end gaps is the most critical failure mode that can limit the ductility of the brace in compression. Up to this failure, the bonded and unbonded regions of the braces performed as designed. The results demonstrated the different deformation and stiffness behaviors of the braces in tension and compression. Subsequent loading to large tension displacements provided evidence of the large energy dissipation that can be expected if premature failure of the brace can be prevented. Simplified numerical models provided good predictions of the measured brace behavior until failure. This research featured the first set of tests for this brace, and the results highlighted adjustments needed to design and modeling to achieve the desired behavior of the brace. Recommendations for future research include improved shear dowel and confinement designs to prevent local buckling of the energy-dissipation bars and improved longitudinal reinforcement designs to prevent yielding of the energy-dissipation bars in the middle bonded region of the braces. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Axial compressive performances of stiffened composite panel were studied in this manuscript. In experimental study, buckling phenomenon of three specimens appear at 413kN, 403kN and 403kN respectively while catastrophic failure appears at 964kN, 934kN and 970kN respectively. Thus average failure load is 2.35 times average buckling load, which indicate the large postbuckling capacity. Only local buckling appears in skin bay without buckling in stiffeners. Buckling strain and failure strain were proposed by the average value of several typical position strains at buckling and failure moment respectively. Average failure strain is −6483 μ ε , which is 2.75 times buckling strain (-2354 μ ε). The relationship between buckling and failure strain is similar to that of buckling and failure load. Failure modes contain debonding and fracture of stiffeners, the splitting and wrapped skin. In numerical study, finite element model considering the Hashin damage, cohesive element and geometry imperfection were built. Buckling load and failure load by FE results have −1.2% and −3.9% error compared to experimental ones, indicating the FE results have good accuracy. FE results show that debonding initiation is close to the moment of final catastrophic failure, about 92.7% failure load. Moreover, debonding area percentage have an accelerating increase trend with the compressive load increasing. [ABSTRACT FROM AUTHOR]

This paper describes a numerical investigation on the seismic design and behavior of a novel reinforced-concrete buckling-restrained brace component for use in precast concrete lateral-load-resisting frames. The design procedure aimed to develop a brace with ductile behavior under reversed cyclic loading. Nonlinear finite element analyses were conducted to investigate the following potential undesirable failure modes of the brace: global buckling of the brace, closure of the end gaps, and local translational buckling of the energy-dissipation bars. The results indicated that failure through global buckling is unlikely for practical brace designs. Closure of the end gaps can be prevented by designing a wide-enough gap at each end of the brace, but design must also ensure that local buckling of the energy-dissipation bars does not occur over their unsupported length across the end gaps. An axially decoupled steel shear dowel can be used to permit a wider end gap without triggering translational buckling of the energy-dissipation bars. Braces that are designed to prevent undesirable failure modes can provide stable behavior up to ductile low-cycle fatigue fracture of the energy-dissipation bars. [ABSTRACT FROM AUTHOR]

This paper aims to carry out comprehensively the static bending, free vibration, and buckling analyses of two-layer FGM plates with shear connectors resting on elastic foundations, where two-layer FGM plates resting on Winker's-Pasternak elastic foundations taking into account relative sliding movements are analyzed by using the combination of Navier's solution and finite element method based on nth -order shear deformation plate theory. The plate is made up of two layers of FG materials joined by metal shear connectors. Lagrange and Hermitian shape functions are used to establish stiffness matrices, mass matrices, geometric stiffness matrices, and element force vectors. The suggested method and mechanical model are accurate when compared to the computed data from this research and reputable literature. The computed data accurately describes the mechanical response of the structure. Then a series of parameter investigations are conducted to capture the effects of the structure's geometrical and material features on the mechanical behavior of two-layer FG plates. The numerical results of this study may be utilized as a basis for future research, applications, and design of similar structures in mechanical and civil engineering practice. This is also a critical foundation for studying the dynamic behavior of structures with shear connectors. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Despite the simplicity of the Duffing oscillator, its dynamical behaviour is extremely rich. Hence, the Duffing equations are used to describe the dynamic behaviour of many real-world nonlinear systems for a wide range of frequency bands and amplitude of the excitation signal in basic sciences and engineering. For example, the Duffing oscillator has been successfully used to model a variety of physical processes such as stiffening springs, beam buckling, nonlinear electronic circuits, superconducting Josephson parametric amplifiers, and ionisation waves in plasmas etc. Therefore, the identification of the Duffing oscillator model/parameters directly from the measured input–output data is a topic of active research in many scientific fields In this paper, we use the concept of stochastic differential equations (SDEs) to identify a model of the Duffing oscillator. SDE-based grey-box models allow us to capture the underlying mathematical structure describing the physics of the system (e.g. the original Duffing equations) using the drift term and explicitly handling of model uncertainty (or the process noise) using the diffusion term whereas the measurement uncertainty is modelled using the measurement noise term respectively. In this paper, we propose a slight variation of the maximum likelihood estimation framework used for the identification of SDEs based grey-box models yielding improved performance for long-term predictions. The proposed framework is combined with an iterative residual analysis to develop a grey-box model of the forced Duffing oscillator. The benchmark data from the so-called Brussels "Silverbox system", which is an electrical circuit mimicking the forced Duffing oscillator dynamics is used for the identification purpose. Finally, the identified model performance (the simulation errors) is compared with the existing results available in the literature. • The likelihood function of the SDE is modified for long-term predictions. • An iterative residual-based method to develop physical-stochastic models is presented. • Modified likelihood function is used for modelling the Duffing Oscillator. • Competitive results are obtained on the "Silverbox"-benchmark. [ABSTRACT FROM AUTHOR]

• Welding induced buckling was observed during thin plates butt welding with dissimilar materials. • Advanced TEP FE computation with large deformation was carried out to represent welding induced buckling. • Good agreement between computed result and measurement was observed with considering clamping effect. • Clamping can significantly reduce magnitude of out-of-plane welding distortion without change of deformed tendency. Welding induced buckling is generally considered as the most complicated type of out-of-plane welding distortion during thin plate section fabrication, which will significantly influence the fabrication accuracy and cost. Thin plates of 3 mm thickness with dissimilar materials were experimentally butt welded together beforehand, while clamping constraint by fixture jig and additional plate was employed. After cooling down and clamping release, out-of-plane welding distortions were measured, and characteristic of welding buckling behavior can be observed. Advanced thermal elastic plastic (TEP) FE computation with solid elements models of examined butt-welded joints were then carried out. Welding induced buckling can be represented without considering clamping constraint, while much larger difference between computed results and measurement data was obtained. When the influence of clamping constraint employed during welding experiment was considered, good agreement for both deformed tendency and magnitude of out-of-plane welding distortion can be represented. With the clarification of mechanism based on the comparison of longitudinal residual stress, plastic strain as well as shrinkage force, clamping can significantly reduce magnitude of out-of-plane welding distortion, which still could not avoid the occurrence of welding induced buckling, as well as the change of deformed shape pattern. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hoop stresses are produced due to the electromagnetic forces in the winding. Free buckling of winding turns can lead to failure of the transformer. Design issues are a major reason for the catastrophic failure of 11kV/433kV distribution transformers. In a distribution transformer (DT), the LV winding is generally of helical type and is asymmetrical. Asymmetry in the transformer design causes change in the direction and magnitude of the forces. In this work, a comprehensive analysis of the short-circuit forces has been done for a DT with a double-layer helical winding with all three of the limbs modelled and phases energized. The forces are computed using magnetostatic analysis of a 315kVA DT. The transformer has been modelled in 3D CAD software and forces are computed using 3D finite element method (FEM) and the results obtained are compared to that obtained from first principals. The windings are assessed for the presence of hoop stresses in its turns, and along with it the safety factor is computed for free-bucking using von-Mises equivalent. The intent is to find the weak section of the double layer helical winding from short circuit forces a transformer is designed to withstand. Such simulations of energy conversion create a robust and sustainable design, which can prevent catastrophic failure and reduce the environmental impact due to major repairs or replacement of equipment. [ABSTRACT FROM AUTHOR]

In order to reduce the possibility of buckling problems related to the railway ballasted tracks, necessary measurements should be applied to improve the lateral resistance of tracks. There are different procedures for increasing the lateral force resistance of railway tracks that can be implemented using di erent materials to change the size, geometry, and dimensions of track components, especially sleepers. Although several studies have been conducted on winged sleepers, the present study investigates the application of mid-winged sleepers with a modified geometry and a dimension in the form of a novel approach. In this regard, several experimental tests and numerical modeling were conducted on the lateral resistance of conventional and mid-winged sleepers. To this end, single sleeper experiment for lateral resistance of the track panel, consisting of five sleepers, was carried out. The lateral force resistance of tracks was measured through the track panel loading and single sleeper push tests. The results revealed that by changing the conventional track to the mid-winged track, the lateral force resistance would considerably increase. The mid-winged panel tests, single mid-winged sleeper tests, and numerical modeling pointed to a 58%{64% increase in the lateral force resistance of mid-wing track, compared to the conventional tracks. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dalian University of Technology / Dalian Ligong Daxue Xuebao is the property of Journal of Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper applies stacking sequence optimization for maximizing the buckling load of rotationally restrained laminated composite rectangular plates with different boundary conditions resting on an elastic Pasternak foundation subjected to uniaxial and biaxial in-plane static loads. The Mindlin Plate Theory (MPT), which considers the firstorder shear deformation effect, was used to extract the characteristic equations of the plates under in-plane loading, including plate-foundation interaction. The buckling problem of laminated plates was analyzed by the Rayleigh-Ritz method. The aim of optimization was to maximize the buckling load and post-buckling load capacities using Genetic Algorithm (GA) method, and the design variable was the ply orientation. The results showed that the optimal orientation, of the laminated square plate under biaxial in-plane loading in various conditions was 45°, approximately. The existence of a foundation, clamped boundary conditions, and high aspect ratio led to increase in the optimal orientation. [ABSTRACT FROM AUTHOR]

The present study investigates nonlinear buckling and post-buckling behaviors of composite plates with the circular/elliptical cut-out using Particle Semi-Energy (PSE) method. The semi-energy is based on the solution of the compatibility equation obtained from an Airy force and out-of-plane displacement functions. The unknown parameters of these functions were determined by minimizing the potential energy. The integrals of the potential energy were then replaced by the summations at the perforated plate particle (node). The cut-out was easily modeled using these nodes. This method enjoys some advantages, namely easy cut-out modeling by nodes and proposing just one of the displacement fields (i.e., out-of-plane). According to the results, there was good agreement (1.25%) between the post-buckling loads derived from PSE in this paper and the experimental test of the literature. According to the experimental test results, the accuracy of Finite Element Method (FEM) was 7.5%. This study also evaluated the effects of rotating the elliptical cut-out and replacing it with two other circular cut-outs in the same areas on the post-buckling load. [ABSTRACT FROM AUTHOR]

This paper applies stacking sequence optimization for maximizing the buckling load of rotationally restrained laminated composite rectangular plates with different boundary conditions resting on an elastic Pasternak foundation subjected to uniaxial and biaxial in-plane static loads. The Mindlin Plate Theory (MPT), which considers the firstorder shear deformation effect, was used to extract the characteristic equations of the plates under in-plane loading, including plate-foundation interaction. The buckling problem of laminated plates was analyzed by the Rayleigh-Ritz method. The aim of optimization was to maximize the buckling load and post-buckling load capacities using Genetic Algorithm (GA) method, and the design variable was the ply orientation. The results showed that the optimal orientation, 0. of the laminated square plate under biaxial in-plane loading in various conditions was 45°, approximately. The existence of a foundation, clamped boundary conditions, and high aspect ratio led to increase in the optimal orientation. [ABSTRACT FROM AUTHOR]

Unintended slight curvature of a straight pipe and temperature variation in a pipe has been found to create uncertainties in tubes and pipes. Fluttering, divergence, and chaotic instabilities of slightly curved carbon nanotubes (SCCNT) conveying hot pressurized fluid are investigated in this paper. The SCCNT is modeled on the basis of large deformation strains. Their gradients are included in the strain energy expression and the velocity and its gradients in the kinetic energy derivation. In modeling the size effects, both the static and kinetic length scales in the energy equations were considered. Governing equation is derived using Lagrangian approach. The effects of geometric imperfection (which leads to cusp bifurcation), small length scale, and kinetic material length parameter on the static and dynamic instability characteristics of the pipes are studied. Analysis is performed using the eigenfunction expansion method. It is found that the material length scale parameter increase tends to shift instability to the lower fluid velocity while the kinematic material length parameter increase does not change the buckling point but lowers the frequency. In the nonlinear dynamic case, both the parameters lead to chaos of the nanotube beyond the critical fluid velocity. The thermal loading changes the sudden supercritical pitchfork bifurcation to cusp bifurcation. The increasing linear and nonlinear foundation stiffness leads the system to chaotic features after the critical point. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An important step in turbine repair is the re-contouring process as it determines part and surface properties. Re-contouring is performed subsequently to the material deposit and has to be adapted to each repair case individually. Especially, part distortion is a crucial aspect in terms of quality and has to be considered in process design. This paper introduces a novel method for evaluation of re-contouring processes regarding part quality and, especially, part distortion. For this purpose, a simulation model for calculating local cutting conditions is introduced and validated experimentally. The validation is carried out for a thin-walled analogue part. The results reveal a clear dependency between the absolute part distortion and the surface generating cut volume (SGCV). [ABSTRACT FROM AUTHOR]

Suspen-dome structures are widely used due to their superiority over traditional structures. The cable condition is crucial for the safety of the overall structures, especially the force in cables. However, to date, no accurate and efficient numerical method can be used for estimating the influence of friction. In this paper, a series of novel numerical methods were proposed and incorporated into a numerical model of the suspen-dome structure. The influence of friction on buckling capacity and dynamic response of suspen-dome structures was analyzed. Results indicated that the dynamic response is significantly influenced by friction. The numerical model that considers friction can be established efficiently in an overall structure model based on general finite element software and can be adopted for dynamic analysis. The buckling capacity can be maximized in the non-sliding condition. The fixation of the hoop cable located in the outer part of the structure has limited influence on the improvement of buckling capacity. For seismic analysis, the varying amplitude of cable force in non-sliding conditions was approximately two times that in sliding conditions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fibrous reinforcements for structural composites manufacturing need to undergo in certain cases a complex shape forming process during which multiple defects could appear. These defects, such as tow buckling and tow sliding may reduce the integrity of the final part. The onset of these defects depends on the initial loading conditions, the shape of the preform and the characteristics of the textile material. While mechanisms behind the formation and development of both defects are yet to be fully understood. We focused, in this work, on investigating the buckling defect. In order to do so, we used optical field measurement techniques to monitor the kinematics of the defect appearance and predict it via an adapted analytical model of the defect appearance. [ABSTRACT FROM AUTHOR]

The overground parking lot including a robot-driven elevator has the advantage of complete automation. The parking lot can be attended to, in case of an emergency, by auxiliary elevators that operate several small-sized side platforms that can transport vehicles between the parking floors. These elevators can be operated by mechanisms provided with translating cams and roller translating followers. In order for the follower rod to withstand buckling, it is required that we be in the elastic field and the Euler formula be applicable. Calculation of the buckling critical load of a rod pertaining to a roller translating follower. [ABSTRACT FROM AUTHOR]

Compression tests on twenty unidirectional (UD) carbon fbre reinforced plastic (CFRP) specimens are conducted, the statistics on the measured compreesive strength is calculated, and the fracture surface is characterized. Two types of different fracture surface are experimentally observed, and they are corresponding to very diferent values on the compreesive strength. A fnite element (FE) analysis is conducted to investigate the infuence of random fbre packing on the compreesive strength. And a riks method (provided in ABAQUS software) is applied in FE model to analyze fbre buckling behaviour in the vicinity of compreesive failure. The FE analysis agrees well with the experimental observation on the two types of buckling modes and also the partition of compreesive strength. It is clearly shown that the random fibre packing lays a significant infuence on the random variability of compressive strength of CFRP. [ABSTRACT FROM AUTHOR]

This work deals with an eigenbuckling analysis for the case of different cross-section straight slender beams having pretwist, in the case of axial compression loads. The study is interesting when the beam cross-section has different moments of inertia with respect to two normal axes, as the pretwist leads to a coupling effect between the weak and strong bending planes. Several cases are analysed in order to find possible optimum pretwist angle in order to increase the buckling loads. The numerical computations, performed in ANSYS finite element code, use different element types as beams, shells or solids in order to obtain better modelling. Discussions on the applied loads, boundary conditions and other aspects of the finite element modelling are also presented. [ABSTRACT FROM AUTHOR]

Abstract In this paper, shapes of nonlinear blood vessels, surrounded by nonlinear soft tissues, and buckled due to radial pressure are solved for analytically and numerically. The blood flow rates through the bucked shapes are then computed numerically. A Fung-type isotropic hyperelastic stress-strain constitutive equation is used to establish a nonlinear mathematical model for radial buckling of blood vessels. The surrounding tissues are modeled as non-linear springs. Novel formulas for critical buckling pressures are derived analytically from the bifurcation analysis. This analysis shows that the nonlinearity of vessel's wall increases the critical buckling pressure. A numerical differential correction scheme is introduced to solve for post-buckling shapes. And the corresponding blood flow rates are provided before touching of the collapsed walls. The blood flow rate through a one-point wall-touching case is also provided. Numerical results show that both vessel's wall and soft tissues nonlinearities increase, locally, the flow rate through the buckled blood vessels. More importantly, a nonlinear relation between blood flow rate and the soft tissue spring constants is found. [ABSTRACT FROM AUTHOR]

Abstract Over the past two decades, buckling-restrained braces (BRBs) have become increasingly popular as a lateral resisting system because of their capability to provide energy dissipation, stiffness and strength to building structures. Up to date, the Egyptian code has no specifications for estimating the response modification factor (R-factor) of structures equipped with BRBs. The only available alternative for BRB design is to use the R-factor of conventional bracing which is equal to 4.5. This study evaluates the R-factors of low– to mid-rise buckling restrained braced frames (BRBFs) designed according to the Egyptian code. Three BRBFs with 3-, 6- and 12-stories are designed with an R-factor of 4.5. The actual R-factors of the frames are evaluated by conducting static pushover and earthquake time history analyses. The results obtained indicate that the R-factors of the BRBFs considered in this study vary from 5.0 to 13.5 in case of static pushover analysis and from 6.7 to 9.1 in case of earthquake analysis. These static and dynamic ranges of the R-factor are higher than the R-factor of 4.5 specified by the Egyptian code for the design of braced steel frames. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a numerical procedure using finite element analysis for the calculation of axial strength of cold formed steel built-up I-sections composed of two back-to-back channels or stiffened web sigma (Σ). The material nonlinearity of the plane and curved parts of the section were considered in the model. The effects of initial local and global geometric imperfections as well as the membrane residual stresses have been taken into consideration in the FE model. The results of the nonlinear FEA were compared with the available experimental data, and with the calculated theoretical buckling capacities based on the AISI design provisions. A parametric study was performed using the developed FE model to investigate the effects of member and geometries and imperfection values on the capacity of CFS built-up I-columns. A comparison is performed between the member's axial capacities results from the parametric study and the design capacities calculated using the AISI. The results of the parametric study state that the design specification noted in the AISI are generally conservative for long and medium length columns, but may give un-conservative estimates for some of the short columns. [ABSTRACT FROM AUTHOR]

As a type of expansive soil, black cotton soil swells when absorbing water and shrinks when dehydrated, and the cycle of swellingshrinking movements can readily occur repeatedly. These characteristics result in serious consequences both to land surfaces and to surface buildings such as ground fracturing, building settling, and road buckling and cracking, having extreme adverse effects on the quality and safety of road transportation. With Kitui, Kenya as the research area and a GF-1 remote sensing image as the vector, this study focuses on in-depth exploration of the application of a deep belief network to identify and classify black cotton soil based on the characteristics of the local black cotton soil in the remote sensing image. The results indicate that given the sample database available to this study, when the network depth was 3, the number of nodes in each hidden layer was 60, the learning rate was 0.01, the number of iterations was 20, and the number of samples was 2,000,000. The best classification result could be achieved with a precision of about 90% per the evaluation criteria proposed in this study, indicating a significant advantage of the deep belief network in remote sensing identification of black cotton soil. [ABSTRACT FROM AUTHOR]

In service pipelines exhibit bending loads in a variety of in-field situation. These bending loads can induce large longitudinal strains, which may trigger local buckling on the pipe's compressive side and/or lead to rupture of the pipe's tensile side. In this article, the post-buckling failure modes of pressurized X65 steel pipelines under monotonic bending loading conditions are studied via both experimental and numerical investigations. Through the performed full-scale bending test, it is shown that the post-buckling rupture is only plausible to occur in the pipe wall on the tensile side of the wrinkled cross section under the increased bending. Based on the experimental results, a finite element (FE)-based numerical model with a calibrated cumulative fracture criterion was proposed to conduct a parametric analysis on the effects of the internal pressure on the pipe's failure modes. The results show that the internal pressure is the most crucial variable that controls the ultimate failure mode of a wrinkled pipeline under monotonic bending load. And the post-buckling rupture of the tensile wall can only be reached in highly pressurized pipes (hoop stress no less than 70% SMYS for the investigated X65 pipe). That is, no postwrinkling rupture is likely to happen below a certain critical internal pressure even after an abrupt distortion of the wrinkled wall on the compressive side of the cross section. [ABSTRACT FROM AUTHOR]

It is generally accepted that the presence of imperfections in pressure vessel components can significantly reduce their buckling strength. In fact, the discrepancies between theoretical predictions and experimental results have been attributed to various kinds of existing and unavoidable imperfections. This is not a new problem but despite of substantial research effort in this area over the recent decades, it is far from being satisfactorily resolved. This review provides insight into the past findings and current activities related to the role of different types of imperfections on the buckling strength. It aims to contribute to a better understanding of the influence of imperfections on the structural stability of cones, cylinders, and domes when these are subjected to external loading conditions. The review concentrates not only on the prominent role of initial geometric imperfections of the shell's generator but also on less known defects. This includes uneven axial length of cylinders, eccentricities, and nonuniformities of applied load, inaccurately modeled boundary conditions, corrosion of the wall, influence of material discontinuity or crack, and effect of prebuckling deformation. The study examines: (i) how the data were obtained (analytically, experimentally, and/or numerically), (ii) the type of material from which the shell structures were made, and (iii) the importance of findings of the previous works. Metallic and composite components are considered. [ABSTRACT FROM AUTHOR]

In this paper, dynamic buckling of the smart subjected to blast load subjected to electric field is studied. The sandwich structure is rested on Pasternak foundation with springs and shear elements. Applying piezoelasticity theory and hyperbolic shear deformation beam theory (HSDBT), the motion equations are derived by energy method. For calculating the dynamic instability region (DIR) of the sandwich structure, differential quadrature method (DQM) along with Bolotin method is used. The aim of this study is to investigate the effects of applied voltage, geometrical parameters of structure and boundary conditions on the DIR of the structure. The results show that applying negative voltage, the DIR will be happened at higher excitation frequencies. In addition, the clamped-clamped beam leads to higher excitation frequency with respect to simply supported boundary condition. [ABSTRACT FROM AUTHOR]

An experimental study followed by comprehensive flow modeling is presented. The experiments were conducted on a horizontal annulus with drillstring under compression, considering the influence of rotation on frictional pressure losses of yield-power-law (YPL) fluids. Flow through various buckling configurations with and without drillstring rotation was investigated. Correlations of critical Reynolds numbers are presented that predict the onset and offset of transition from laminar- to turbulent-flow regions in concentric and eccentric annuli. A broad model of flow of YPL fluids is proposed for concentric, eccentric, and buckled configurations. The model includes the effects of rotation in laminar, transitional, and turbulent flow. A 91-ft inner pipe was rotated while applying axial compression during flow. At the no-compression case, eccentricity of the inner pipe is varied as the drillstring rotated. The aim for such a design was to simulate actual drilling operations. The test matrix involves flow through sinusoidal, transitional, and helically buckled drillstring. The effect of pitch length is investigated. Helical modes with two different pitch lengths were tested. Eight distinct YPL fluids were used to examine the dependence of pressure losses on fluid parameters. In the theoretical part, a stability criterion is modified to determine the onset of transitional flow of YPL fluids and a correlation is proposed for practical purposes. In addition, pressure-loss-prediction models are presented for the flow of YPL fluids through concentric, eccentric, free, and buckled configurations of the drillstring, with and without rotation. The proposed models are compared with data from the literature and the experiments. It has been observed that increasing eccentricity and rotary speed causes an earlier transition from laminar to turbulent flow. Results suggest reduced pressure losses with an eccentric pipe. In addition, buckled configurations showed a further decrease of frictional pressure losses as the compression increases. In the helical mode, two pitch lengths are compared, and decreasing the pitch length resulted in a decrease in pressure losses. Rotation tests are conducted with free and buckled configurations. Rotation in the free-drillstring mode showed an increase in pressure losses as the rotary speed of the drillstring increases. Amplified vigorous motion of the drillstring is visually observed as the drillstring is buckled while rotating. Rotating the drillstring while buckled showed a further increase in pressure losses compared to rotating in free mode. This additional increase in pressure losses is attributed to the more-dynamic motion of the drillstring. Distinct differences of pressure losses in the effects of buckling and rotation are observed in laminar, transitional, and turbulent flow. Significant differences are measured in the transition region. [ABSTRACT FROM AUTHOR]

The structural integrity of underground pipelines are subject to a major threat from permanent ground displacements when they cross active tectonic (e.g., strike-slip) faults, because of large strains potentially induced in pipes, leading to pipe buckling and possible rupture. In this paper, the buckling behavior of X80 pipe is studied numerically with an emphasis on the effects of steel stress-strain characteristics. A rigorous mechanics-based nonlinear finite element (FE) model of a buried X80 pipe crossing a strike-slip fault is developed using shell elements and nonlinear springs for the pipe and soil resistance, respectively. The pipe steel material in the FE model is characterized by a novel and versatile stress-strain relationship, which was established to successfully capture both the round-house (RH) type and the yield-plateau (YP) type stress-strain behaviors. This allows investigating the significant effects of the stress-strain characteristics, as observed in this paper, on the buckling behavior of pressurized and nonpressurized pipes. [ABSTRACT FROM AUTHOR]

Although the inner container of the cryogenic liquid semitrailer works under inner pressure, it needs to be vacuumed during the helium leak detection. Furthermore, the inner container usually cannot meet the stability requirements during the evacuation, though equipped with stiffening structures such as supporting rings for baffles inside the container. Therefore, a kind of temporary local rigid clamping structure was proposed to improve the antibuckling ability of the inner container during the helium leak detection. "Lulu" can was taken as the thin-walled cylindrical shell specimen under external pressure and was clamped with the temporary local rigid ring on the outside surface. The critical pressures were experimentally and numerically studied for the specimen with local clamping rings of different sizes, in which eigenvalue buckling analysis and nonlinear analysis were employed with the aid of ANSYS. It indicates that the critical pressure of the specimen with the local clamping ring is higher than that without the clamping ring. Finally, the optimal clamping scheme including size and location of clamping rings for the inner container of DC18 type cryogenic liquid semitrailer was studied with the finite element method, which aimed to improve the antibuckling capacity of the inner container during the helium leak detection. [ABSTRACT FROM AUTHOR]

In this paper, a novel simple shear deformation theory for buckling analysis of single layer graphene sheet is formulated using the nonlocal differential constitutive relations of Eringen. The present theory involves only three unknown and three governing equation as in the classical plate theory, but it is capable of accurately capturing shear deformation effects, instead of five as in the well-known first shear deformation theory (FSDT) and higher-order shear deformation theory (HSDT). A shear correction factor is, therefore, not required. Nonlocal elasticity theory is employed to investigate effects of small scale on buckling of the rectangular nano-plate. The equations of motion of the nonlocal theories are derived and solved via Navier's procedure for all edges simply supported boundary conditions. The results are verified with the known results in the literature. The influences played by Effects of nonlocal parameter, length, thickness of the graphene sheets and shear deformation effect on the critical buckling load are studied. Verification studies show that the proposed theory is not only accurate and simple in solving the buckling nanoplates, but also comparable with the other higher-order shear deformation theories which contain more number of unknowns. [ABSTRACT FROM AUTHOR]

A new concept is proposed in the local tubular mechanical model, which provides a more-sophisticated description of tubular mechanical behaviors from a local perspective. The principles and assumptions for the local mechanical model are presented. Under these assumptions, the mechanical behaviors of tubular strings with connectors under nonbuckling/lateral-buckling, interhelical-buckling, and intrahelical-buckling modes in vertical and inclined wellbores are studied. The critical interhelical-buckling and intrahelical-buckling loads are deduced with the assumed load-displacement curve and potential-energy factor. The contact states under every buckling mode are divided into no contact, point contact, and wrap contact, and the critical contact loads are deduced with critical contact conditions. The results of critical buckling loads, critical contact loads, contact forces, and maximum bending moments are compared, and these results are given in explicit forms for the convenience of application. The results show that buckling mode transforms from nonbuckling/lateral buckling to interhelical buckling to intrahelical buckling, and contact state transforms from no contact to point contact to wrap contact with the increase of axial force. The effects of connectors on buckling behaviors are determined by both the geometric and mechanical parameters of tubular strings with connectors. Connectors can inhibit the buckling problem and increase the axial force and torque transfer, but may increase the possibility of tubular failure. Therefore, these two effects of connectors should be considered comprehensively in the optimal design of connectors on tubular strings. [ABSTRACT FROM AUTHOR]

Multistage cylinders are generally used to lift and tilt heavy loads under controlled speed. In defence applications multistage cylinders are used in missile tilt platform and antenna mast. Earth moving equipment's such as tippers, dumpers, cranes and compactors uses multistage cylinders for operations. In the present work multistage hydraulic cylinder (telescopic cylinder) with three stage has been analysed using strain energy method and verified with finite element analysis. The research work investigates the effect of internal clearances which reduces the critical buckling load of hydraulic cylinders. The results are validated by buckling load test. The clearances between the tube to piston guides, gland guide to piston rod, clearances due to tube expansion under pressure, initial curvature in the tube, eccentricity of cylinder components and tube ovality are considered in the buckling load test. Describes the comparative study of buckling load tests of three stage hydraulic cylinders having fixed free and hinged mounting with five different internal clearances. [ABSTRACT FROM AUTHOR]

This work presents the buckling investigation of embedded orthotropic nanoplates such as graphene by employing a new refined plate theory and nonlocal small-scale effects. The elastic foundation is modeled as twoparameter Pasternak foundation. The proposed two-variable refined plate theory takes account of transverse shear influences and parabolic variation of the transverse shear strains within the thickness of the plate by introducing undetermined integral terms, hence it is unnecessary to use shear correction factors. Nonlocal governing equations for the single layered graphene sheet are obtained from the principle of virtual displacements. The proposed theory is compared with other plate theories. Analytical solutions for buckling loads are obtained for single-layered graphene sheets with isotropic and orthotropic properties. The results presented in this study may provide useful guidance for design of orthotropic graphene based nanodevices that make use of the buckling properties of orthotropic nanoplates. [ABSTRACT FROM AUTHOR]

In this article, an exact analytical solution for mechanical buckling analysis of magnetoelectroelastic plate resting on pasternak foundation is investigated based on the third-order shear deformation plate theory. The in-plane electric and magnetic fields can be ignored for plates. According to Maxwell equation and magnetoelectric boundary condition, the variation of electric and magnetic potentials along the thickness direction of the plate is determined. The von Karman model is exploited to capture the effect of nonlinearity. Navier's approach has been used to solve the governing equations for all edges simply supported boundary conditions. Numerical results reveal the effects of (i) lateral load, (ii) electric load, (iii) magnetic load and (iv) higher order shear deformation theory on the critical buckling load have been investigated. These results must be the analysis of intelligent structures constructed from magnetoelectroelastic materials. [ABSTRACT FROM AUTHOR]

Yield and buckling are independent of hydrostatic pressure. However, leak in a threaded connection depends on hydrostatic pressure, and hence, leak resistance is a function of connector location in the string. It also means that von Mises stress alone is insufficient to characterize connection leak. Like pipe-body yield and buckling, a simple consistent failure theory derived from principles of mechanics is proposed for leak in threaded connections. In addition, the buckling fictitious force is reformulated as a nonfictitious expression to clearly show independence of hydrostatic pressure. Two leak constants--thread modulus and makeup leak resistance--are introduced and evaluated with simple example cases. To quantify results, a 7-in. long-thread-casing (LTC) connection is modeled with the new leak criterion, and results demonstrate that the connection can withstand differential pressures higher than the published ratings because of hydrostatic pressure. A new connection safety factor is defined, and a leak line and a leak circle are developed for graphical purposes to quickly identify critical loads for leak. [ABSTRACT FROM AUTHOR]

The seismic resistance of a 36-storey high-rise structure with the height of 149 m is studied in this paper. The simulated earthquake shaking table tests have been performed on 1/20 scaled model of the steel-concrete hybrid structure. The steel-concrete hybrid structure is composed of the surrounding diagrid, the reinforced concrete core tube, the floor slab, the beam of floor. The dynamic properties and the seismic behaviour have been analysed by the shaking table test based on the measurement method on the natural vibration frequency and the damage of the model structure. The test results have shown that the phenomena of failure occurred in some components after undergoing the earthquakes of the different fortification levels. The buckling failures occur in the inclined column of the diagrid on the higher floors, the horizontal cracks in the core walls of the higher floors has been appeared, and also the damages occur in the connection between the concrete core tube, the inclined beam of floor and the span beam. Since these inclined column and the key joints between the concrete core tube and the beam have been damaged seriously in the shaking table test, the detailed theoretical analysis is required to avoid the local structural damage. [ABSTRACT FROM AUTHOR]

In recent years, high strength steel has gradually attracted the attention of the construction industry, due to its high yield strength, tensile strength, good performance of resistance to brittle failure and high reliability of structures. Common finite element ABAQUS software is employed in this paper to simulate the lateral torsional buckling of Q460 welded beams. Finite element analysis models considering initial geometric imperfections were conducted. Besides, parametric studies were carried out to evaluate the effect of key parameters on the global stability behavior of Q460 beams as well. And the results obtained from finite element analysis simulations were compared with the design buckling curves from Chinese steel structure design codes (GB50017-2003, GB50017-201X) and AS4100. Finally, new design buckling curves are presented in this paper in order to evaluate the global stability behavior of Q460 steel beams. [ABSTRACT FROM AUTHOR]

The bottom slender columns are widely used in modern high rise buildings because of the existence of floor with opening, and the effective length will deeply affect bearing capacity of the column. This paper presents a new methodology for calculate the effective length of the bottom slender columns based on the equivalent model. The elastic restraints of beams are considered as lateral support spring, and the effective length of the column is determined through buckling analysis of the column fixed at bottom and elastic supported at top. A case study of high rise building with 20 m bottom slender column was conducted as follows: A horizontal force was applied on the floor supporting of the slender column top, and the lateral displacement of the column could be calculated through whole structure analysis in design procedure, therefore, the spring stiffness can be figured out through the applied horizontal force divided by the displacement. Then, eigenvalue buckling analysis was conducted on the column by using software ANSYS. The buckling mode shape were checked and the lowest buckling mode was solved, the buckling critical load could be obtained by multiplying the critical load coefficient by compression stress of the member. Finally, the effective length factor could be determined by comparing the bearing capacity of the bottom slender column with bearing capacity of that column with hinge joint at both ends. The results indicate that the effective length factor of the bottom slender column based on the proposed method is 21% larger than that in the design code. The weakness in bearing capacity of the bottom slender column should be considered during design. [ABSTRACT FROM AUTHOR]

Studies on dissipative metamaterials have uncovered means to suppress vibration and wave energy via resonant and bandgap phenomena through such engineered media, while global post-buckling of the infinitely periodic architectures is shown to tailor the attenuation properties and potentially magnify the effective damping effects. Yet, despite the promise suggested, the practical aspects of deploying metamaterials necessitates a focus on finite, periodic architectures, and the potential to therefore only trigger local buckling features when subjected to constraints. In addition, it is likely that metamaterials may be employed as devices within existing engineering systems, so as to motivate investigation on the usefulness of metamaterials when embedded within excited distributed or multidimensional structures. To illuminate these issues, this research undertakes complementary computational and experimental efforts. An elastomeric metamaterial, ideal for embedding into a practical engineering structure for vibration control, is introduced and studied for its relative change in broadband damping ability as constraint characteristics are modified. It is found that triggering a greater number of local buckling phenomena provides a valuable balance between stiffness reduction, corresponding to effective damping magnification, and demand for dynamic mass that may otherwise be diminished in globally post-buckled metamaterials. The concept of weakly constrained metamaterials is also shown to be uniformly more effective at broadband vibration suppression of the structure than solid elastomeric dampers of the same dimensions. [ABSTRACT FROM AUTHOR]

A containment of a nuclear power plant is a final barrier against the release of radioactive materials and withstands internal pressure due to an accident. Buckling is a critical failure mode of an ellipsoidal head of steel containment vessel under internal pressure. First, a vessel was designed to measure buckling pressure and shape of the ellipsoidal head. Second, an experiment was successfully performed on an ellipsoidal head which has a diameter of 4797 mm, a radius-to-height ratio of 1.728, and a thickness of 5.5 mm. The initial shape and deformations of the ellipsoidal head were measured by using three-dimensional (3D) laser scanners. The detailed buckling characteristics including shapes, deformations, strains of buckles, and buckling pressures were obtained. Finally, initial buckling pressures were predicted by nonlinear finite element analysis considering the initial measured and the initial perfect shapes of the ellipsoidal head, respectively. The agreement between the initial experimental buckling pressure and that predicted by the analysis considering the initial measured shape is good. [ABSTRACT FROM AUTHOR]

Linearized buckling analysis of functionally graded shells of revolution subjected to displacement-dependent pressure, which remains normal to the shell's middle surface throughout the deformation process, is described in this work. Material properties are assumed to be varied continuously in the thickness direction according to a simple power law distribution in terms of the volume fraction of a ceramic and a metal. The governing equations are derived based on the first-order shear deformation theory, which accounts for through the thickness shear flexibility with Sanders type of kinematic nonlinearity. Displacements and rotations in the shell's middle surface are approximated by combining polynomial functions in the meridian direction and truncated Fourier series with an appropriate number of harmonic terms in the circumferential direction. The load stiffness matrix, also known as the pressure stiffness matrix, which accounts for the variation of load direction, is derived for each strip and after assembling resulted in the global load stiffness matrix of the shell, which may be unsymmetric. The load stiffness matrix can be divided into two unsymmetric parts (i.e., load nonuniformity and unconstrained boundary effects) and a symmetric part. The main part of this research is to quantify the effects of these unsymmetries on the follower action of lateral pressure. A detailed numerical study is carried out to assess the influence of various parameters such as power law index of functionally graded material (FGM) and shell geometry interaction with load distribution, and shell boundary conditions on the follower buckling pressure reduction factor. The results indicate that, when applied individually, unconstrained boundary effect and longitudinal nonuniformity of lateral pressure have little effect on the follower buckling reduction factor, but when combined with each other and with circumferentially loading nonuniformity, intensify this effect. [ABSTRACT FROM AUTHOR]